The present invention relates to a method and apparatus for injecting oxygen within an engine. In particular, but not exclusively, the invention relates to injecting oxygen within an engine of a vehicle to allow a greater use of exhaust gas recirculation within the engine.
Exhaust gas recirculation (EGR) is used to reduce the amount of nitrogen oxide (NOx) emissions from petrol and diesel combustions by recirculating a portion of exhaust gas back into the engine cylinders for combustion. NOx forms primarily when a mixture of nitrogen and oxygen is subjected to a high temperature. By displacing an amount of oxygen and combustible materials in the cylinder via EGR, the temperature of combustion can be reduced resulting in lower emissions.
Most modern engines now require exhaust gas recirculation to meet emissions standards. In a typical automotive engine, between 5 to 15 percent of the exhaust gas is typically recirculated back to the air intake. At this level, however, EGR can result in losses in engine performance. For example, EGR measurably slows combustion and excessive EGR can cause high smoke emissions and misfires.
EGR losses are most apparent during specific operating conditions. For example, during steady state conditions, the EGR flow rate is limited to allow sufficient air for fuelling in the event that the driver operates the accelerator pedal. Thus, though higher amounts of EGR could maintain stable operation at steady state, it would not allow for sufficient combustion efficiency to achieve acceleration. Further, in high loads EGR may reduce peak power output. EGR is also conventionally not used at idle speed because it may contribute to unstable combustion.
The inventors found that by introducing oxygen into the EGR system in response to the actuation of an accelerator device, EGR can be maintained at higher levels and the lack of oxygen for combustion may be compensated. Thus efficiency losses from EGR during acceleration may be reduced or eliminated.
In a turbocharged engine, a turbocharger may include a compressor to compress air intake from the atmosphere or an exhaust gas recirculation system, to be delivered to the engine for combustion. By increasing the mass of air entering the engine, the expansive power of combusted energy is increased resulting in increased available torque and thus power and efficiency.
A compressor may be coupled to a high speed turbine within the exhaust system. A turbine may convert the kinetic energy and the potential energy from pressure into work that may be delivered to the compressor to provide power.
Boost from a turbocharger may be responsive to operating conditions and may be initiated to achieve acceleration. The initiation of turbocharge may be referred to as turbo boost. In systems that initiate turbo boost in response to throttle change, achieving boost requires first initiating the energy conversion capabilities of the turbine, accumulating of an amount of work, delivering accumulated work to the compressor, compressing intake aircharge, then delivering compressed air intake to the engine for combustion. The delay between throttle actuation and combustion of boosted aircharge to the engine is called turbo lag.
Turbo lag may be perceived by the operator as hesitation in the throttle response when accelerating from an idle speed. Turbo lag decreases the responsiveness of the vehicle to the operator and thus driving comfort and control.
The inventors found that by including a hydrogen delivery apparatus adapted to deliver hydrogen to the exhaust gas system such that the hydrogen can combust and expand, turbine speed may increase and turbo lag decrease. Further, by delivering hydrogen to the exhaust system upstream of the turbine where exhaust gas is relatively oxygen rich, the combustion of hydrogen may be assisted. The oxygen available for hydrogen combustion may be controlled or responsive to the activation of a turbo charger and may be provided by an oxygen delivery apparatus.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.